This study was undertaken to assess a new method for the non-invasive determination of cerebral blood flow without the use of radioactive tracers. Specifically, we used a new 19F NMR technique to measure the clearance of a fluorinated inert gas, CHF3, from the brain. We tested the new technique by comparing the cerebral blood flow values determined by 19F NMR with cerebral blood flow values determined simultaneously by radioactive microsphere techniques. The cerebral blood flow values determined by 19F NMR and radioactive microsphere techniques agreed reasonably well, and showed the same response to variations in the arterial C02 level. We conclude that the 19F NMR technique gives a quantitative measure of cerebral blood flow. In the last year we used NMR imaging techniques to localize the 19F NMR spectra (and thus the blood flow measurement) to a well defined region of the brain. We also began a series of experiments that combines 19F NMR determination of the cerebral blood flow (and oxygen consumption) with 31P NMR determination of cerebral energetics.